A typical horizontal axis wind turbine is illustrated in FIG. 1. The wind turbine 1 comprises a tower 2, a nacelle 3 mounted on top of the tower 2 and a rotor 4 operatively coupled to a generator 5 within the nacelle 3. The wind turbine 1 converts kinetic energy of the wind into electrical energy. In addition to the generator 5, the nacelle 3 may house the various components required to convert the wind energy into electrical energy and also the various components required to operate and optimize the performance of the wind turbine 1. The tower 2 supports the load presented by the nacelle 3, the rotor 4 and other wind turbine components within the nacelle 3.
The rotor 4 includes a central hub 6 and three elongate rotor blades 7a, 7b, 7c of approximately planar configuration that extend radially outward from the central hub 6. In operation, the blades 7a, 7b, 7c are configured to interact with the passing air flow to produce lift that causes the central hub 6 to rotate about its longitudinal axis. Wind exceeding a minimum level will activate the rotor 4 and allow it to rotate within a plane substantially perpendicular to the direction of the wind. The rotation is converted to electric power by the generator 5 and is usually supplied to the utility grid.
The turbine blades have a root section at which it connects to the central hub. The root section is generally circular in cross section and for blades which are 80 m or more in length can be as much as 4 or 5 meters in diameter. At the opposite end of the blade to the root is the blade tip. The direction along the blade between the root and the blade tip is known as the span-wise direction. In the lateral direction, known as the chord-wise direction, the blade extends between a leading edge and a trailing edge.
FIG. 2 shows an example rotor blade construction, with the exploded perspective view in FIG. 2 showing the elements used in the construction of such a rotor blade. The rotor blade is formed from two half shells 202 and 206 which each comprise elongate reinforcing structures 204. The two reinforcing structures that extend substantially along the full length of the turbine blade from the root section to the blade tip are referred to as spar caps. The complete turbine blade is formed from the two half shells 202 and 206 and two shear web 205 placed in between. The shear webs 205 are used to couple together the spar caps in order to transfer shear forces.
The shear webs are formed from first and second shear web panels that need to be aligned with one another. Since the blade may be up to 80 m long, or more, the shear webs are preferably formed from a number of segments of corresponding shear web panels. For example, the segments may be formed of shear web panels that are around 10 m or 11 m in length, so that they fit in a standard transport container. It is possible to form the shear web panels with a connecting element between them, in a so called “top hat” or substantially “U” shaped arrangement. This has the advantage that the shear web panels can be manufactured and maintained in alignment with each other. Unfortunately, the use of a connecting element between the shear web panels is not practical at the root of the blade due to the large size of resulting top hat arrangement. Therefore, the larger shear web panels found nearer to the blade root need to be separately installed and aligned with each other during the manufacture of the blade.
Aligning adjacent shear web panels with each other can be a time consuming process, which must take place at the time critical final stages of assembly of the blade, during which a number of process are being undertaken at the same time.
Therefore it is desirable to provide a method of aligning shear web panels for insertion into a wind turbine blade in an easy manner and that avoids the problem of having to perform time consuming alignment within the blade itself.